1. Field of the Invention
The present invention relates to the operation of a closure normally driven by an electric motor and, more particularly, to an override device for allowing manual operation thereof.
2. Description of the Prior Art
It is well known in the art of closures operated by way of electric motors to provide each system with an override device to permit manual operation of the closure in the event, for instance, of a failure of the electric motor. Safety-wise, such an override system must also prevent the motor from operating during the manual opening or closing of the closure.
Canadian Patent No. 1,165,785 issued on Apr. 17, 1984, for instance, discloses the basics of such an override device of the prior art.
More particularly, with reference to FIGS. 1 and 2 of the aforementioned Canadian Patent, a door operator 10 comprises an electric motor 11 adapted to drive a V-belt pulley 12 mounted on the motor shaft which in turn drives, by way of a V-belt 15, a larger V-belt pulley 13 provided on an intermediate shaft 14. A chain drive 16 connects the intermediate shaft 14 to an intermediate sprocket 17 mounted on shaft 18 while a further chain drive 19 joins the shaft 18 to a drive sprocket 20 which operates an output shaft 21. The output shaft 21 which is supported on two pillow blocks 22 mounted on frame members 23 is adapted to open and close a closure, such as a garage door or the like.
A control box 25 is mounted on the frame members 23. The motor shaft is provided with a brake 27 which is operated by a lever mechanism 28. The lever mechanism 28 is connected to an arm 29 rotated by a shaft 30 entering the control box 25. More importantly with respect to the present invention, a manual release lever 31 provided on the other side of the door operator 10 from the brake 27 comprises a linkage which is not shown for allowing the brake 27 to be manually released when it is necessary to operate the door operator 10 manually.
More particularly, there is provided adjacent the manual release lever 31 a chain sprocket 32 with a chain 33 being engaged thereon for permitting manual operation thereof. When it is desired to manually operate the closure, the manual chain 33 is operated manually with the release lever 31 for the brake 27 being activated. Also, a safety interlock switch 43 is adapted to simultaneously disconnect power to the electric motor 11 in order to prevent the power to be accidentally turned on while the closure is being manually opened or closed.
A solenoid 42 operates in such a way so as to rotate the brake shaft 30, whereby when the electric motor 11 is powered to go in either direction the solenoid 42 is energized thereby causing the brake 27 to be released. The safety interlock switch 43 comprises a linkage, which is not shown, connected to the brake release arm 31 so that, if the door operator 10 is manually used, the safety interlock switch 43 is moved to the “off” position thereof thereby preventing the electric motor 11 from being accidentally switched on.
Therefore, the manual release lever 31 allows the brake 27 to be manually released thereby permitting manual operation of the closure by way of the chain 33 and sprocket 32. The manual release lever 31 also causes the safety disconnect switch to cut the power to the electric motor 11.
Accordingly, it is necessary for manually opening or closing a closure to manually operate both a brake release lever which also disconnects power to the motor, and a chain and sprocket assembly.